1. Field of the Invention
The present invention relates to a paper supply control apparatus in a printer and a paper supply method, and more particularly, to a paper supply control apparatus in a printer capable of controlling the paper supply time in response to variations in the circulation cycle of a photoreceptor belt, and a paper supply method for the same.
2. Description of the Related Art
Referring to FIG. 1, a printer includes a printing portion 10 and a paper supplying portion 30 for supplying a sheet of paper to the printing portion 10.
The printing portion 10 is comprised of a photoreceptor belt 14, a reset device 15, optical scanning devices 16, developers 17, a drying unit 18, and a transfer unit 19.
The reset device 15 includes an exposing device 15a for projecting light onto electrostatic latent images remaining on the photoreceptor belt 14 circulated by a plurality of rollers 11, 12 and 13 to erase the electrostatic latent images, and a charger 15b for charging the photoreceptor belt 14 with a predetermined potential to write new electrostatic latent images on the photoreceptor belt 14.
The optical scanning devices 16 form electrostatic latent images on the photoreceptor belt 14 by scanning light corresponding to image information.
The developers 17 develop electrostatic latent images formed on the photoreceptor belt 14 by the optical scanning device 16, using developing agents.
The drying unit 18 is used when a developing solution mixed with a toner and a liquid carrier element is used as the developing agent. The drying unit 18 absorbs and evaporates the liquid carrier element, which does not participate in forming images, from the photoreceptor belt 14.
The transfer unit 19 transfers images formed with toner on the photoreceptor belt 14 to a fed sheet of paper 31.
The paper supplying portion 30 is comprised of a paper feeding cassette 32, a pickup roller 33 for picking up sheets of paper 31 placed in the paper feeding cassette 32, and a plurality of transfer rollers 35 installed along a paper transfer path 34 ranging from the pickup roller 33 to the transfer unit 19 in the printing portion 10 in order to transfer a picked-up sheet of paper 31.
Reference numeral 40 is a recognition pattern detecting sensor including an optical source 41 and an optical detector 42. As shown in FIG. 2, at a fixed position, the recognition pattern detecting sensor 40 detects passage of a recognition pattern 43 formed at a predetermined position departing from an image writing area D on the photoreceptor belt 14, and outputs a signal indicating the arrival of the recognition pattern 43.
Meanwhile, a sheet of paper 31 must be fed to the transfer unit 19 in accordance with the time when toner images formed on the photoreceptor belt 14 are transferred to the transfer unit 19.
To do this, in the prior art, an engine controller (not shown) sets the time to form images on the photoreceptor belt 14 on the basis of receiving the recognition pattern arrival signal from the recognition pattern detecting sensor 40, and the time required for paper pickup such that they are matched to an image transfer time. The image transfer time is the time it takes to transfer images formed on the photoreceptor belt 14 to a picked-up sheet of paper 31. Thus, the engine controller, which controls the printing portion 10 and the paper supplying portion 30, drives the pickup roller 33 to pick up a sheet of paper 31 at a predetermined paper pickup time after a counted time from receiving the recognition pattern signal. Simultaneously, the engine controller drives the optical scanning device 16 to form images on the photoreceptor belt 14 whenever the counted time is consistent with the image transfer time.
However, a one-time circulation cycle of the photoreceptor belt 14 can be changed according to time. The circulation cycle of the photoreceptor belt 14 can be changed according to variations in power transmitted to the photoreceptor belt 14, a change in ambient temperature, or a change in the total length of the photoreceptor belt 14 due to aging. A variation in the circulation cycle of the photoreceptor belt 14 depending on the above factors can increase with an increase in the total length of the photoreceptor belt 14.
When the circulation cycle of the photoreceptor belt 14 is changed by the above-described factors, the generation interval of the recognition pattern arrival signal is also changed. Consequently, according to the conventional paper pick-up method, the interval between sheets of paper 31 traveling along the paper transfer path 34 is also changed according to a variation in the generation interval of the recognition pattern arrival signal. In particular, when an optical scanning interval for each page and a paper pickup interval corresponding to the optical scanning interval are set to be short to increase printing speed, part of a preceding sheet of paper 31 traveling along the paper transfer path 34 may overlap the following sheet of paper even by a small variation in the circulation cycle of the photoreceptor belt 14, resulting in a printing error.